In a receiver used in a wireless communication system, a Radio Frequency (RF) signal is typically received and down converted to a baseband signal before being decoded.
FIG. 1 is a schematic block view of an existing wideband receiver architecture. The receiver 100 usually includes an antenna 110 which receives a RF signal, an antenna Filter Unit (FU) 120 which filters out outband blocking signal from the received RF signal and a Low-Noise Amplifier (LNA) 130 which amplifies the RF signal with a low Noise Figure (NF). The amplified RF signal is then input to a down-conversion portion (as shown on the right side of the dotted line) for converting the RF signal to base band data. A mixer 140 multiplies the RF signal by an oscillator signal of an Intermediate Frequency (IF) frequency generated by a frequency synthesizer 150 to down-convert the RF signal to an IF signal. The IF signal then passes a Band Pass Filter (BPF) 160 such as an IF saw filter, an image filter and an Anti-alias (AA) filter, and is amplified by another LNA 170. Finally an Analog-to-Digital Converter (ADC) 180 converts the IF signal to baseband data for further processing by e.g. Digital Signal Processor (DSP) devices.
Today, with development of wireless communication technology and increasing demand of higher data rate, the required transmission bandwidth is increasing dramatically. In consequence, the In-channel BandWidth (IBW) requirement for the receiver becomes higher. For example, a multi-carrier architecture has been widely used in designing the receiver, in order to satisfy the IBW requirement without increasing complexity of the receiver. At the same time, due to the rapid deployment of various communication nodes, the electromagnetism environment is becoming more and more complex, which raises the requirement for receiver blocking performance. Especially, the dynamic range of the mixer and ADC needs to be large, and the rejection performance of the antenna filter needs to be high. The requirement is even higher in case of a Multi-Stand Receiver (MSR) which is capable of operating in different frequency bands for different communication standards.
For example, for a MSR BC2 receiver, for −25 dBm in band blocking signal, offset from 800 KHz to 1.6 MHz blocking, if we consider a 3 dB receiver chain NF and 8 dB sensitivity degradation (refer to, e.g. 3GPP TS 37.104 V10.1.0 and 3GPP TS 45.005 V9.5.0), the selectivity requirement will be about 84 dB. The ADC Spurious Free Dynamic Range (SFDR) needs to be larger than 90 dBFS, which is a very high requirement. For outband blocking, if we consider a co-location situation in which the Continuous Wave (CW) blocking level is 16 dBm, in order to make the sensitivity degrade less than 0.1 dB for a Global System Mobile (GSM) system, the selectivity should be larger than 150 dB which is also a very high requirement. Filters need to contribute a lot to rejection in the positions where large blocking signals occurs and can not be efficiently suppressed by the Rx circuit. The high requirement for these components makes the product expensive and bulky.